Effects of Growth Pattern and Dietary Crude Protein Levels During Rearing on Body Composition and Performance in Broiler Breeder Females

Egg production, sexual maturation and egg weight were not affected by growth pattern or crude protein levels during rearing, according to new Dutch research.

The combined effects of growth pattern and dietary crude protein level during rearing (from two to 22 weeks of age) on body composition and performance were investigated in broiler breeder females from 0 to 40 weeks of age by Rick van Emous of Wageningen UR in the Netherlands and colleagues there and at Wageningen University.

In a recent paper in Poultry Science, they explain that day-old pullets (n=768) were randomly allotted to 48 pens according to two growth patterns (standard = SGP and high = HGP) and fed using one of three dietary crude protein levels (high-, medium- or low-CP).

From 19 to 22 weeks of age, feeding level was gradually adjusted to obtain a similar target bodyweight for all birds and then until 40 weeks of age, all birds received similar amounts of a standard breeder diet.

During the rearing period, the HGP pullets were fed a higher feed intake level (6.5 per cent) than SGP pullets. To meet bodyweight targets at 22 weeks of age, feed intake from day 14 onwards had to be increased for the medium-CP (4.6 per cent) and low-CP (10.0 per cent) treatments.

Breast muscle percentages of HGP and SGP pullets were similar at every age although abdominal fat pad at 20 weeks was 0.18 per cent higher for HGP pullets.

Pullets fed the low-CP diet had a lower breast muscle percentage than those fed the medium-CP and high-CP diets (0.46 and 0.85 per cent at week 10; 0.81 and 1.45 per cent at week 20, respectively).

Abdominal fat pads in pullets fed the low-CP diet were 0.18 and 0.22 per cent (week 10), and 0.24 and 0.42 per cent (week 20) higher than the medium-CP and high-CP diets, respectively.

At 40 weeks of age, no effects on breast muscle and abdominal fat pad were found among all treatments.

Egg production, sexual maturation and egg weight were not affected by growth pattern or crude protein levels during rearing.

A low crude protein diet during rearing decreased breast muscle and increased abdominal fat pad, whereas a high growth pattern only increased abdominal fat pad, at the end of the rearing period, concluded van Emous and his colleagues.

They added that decreasing dietary crude protein level seems to be more effective in increasing abdominal fat pad than increasing growth pattern.